There are fetishes for everything. Deep voice, while I don't hear about it much, doesn't seem like it'd be too uncommon. It's one of those things you don't have to talk about to meet someone who can fulfill your needs.

My personal opinion on it is the same as any fetish that hurt someone who doesn't want hurt; whatever floats their boat. To each their own, all of us here should be pretty familiar with that notion

That one, I have never discussed about until now, so it's not common to me. I never forget a voice and can pick out every pitch in a person's speaking voice, so I imagine that this quality can be revered to a certain extent, but rarely on a fetish level.

Deep voice fetish is a new one to me, but considering how stimulating we can find certain sounds (and the fact that different sounds excite/please each unique individual), it doesn't seem a particularly unusual or difficult fetish to understand. I can't say I feel that way myself, but I find certain regional accents or tones of voice particularly pleasant to my ear. I guess a fetish based around voices is essentially a logical extension of that.